It is well known that steel tubulars and equipment used in the production of oil and gas are exposed to corrosive environments. Such environments generally consist of acid gases (CO2 and H2S) and brines of various salinities. Under such conditions the steel will corrode, possibly leading to equipment failures, injuries, environmental damage and economic loss. Further in some cases, drilling fluids have acid intentionally added thereto in order to acidize the formations to enhance hydrocarbon recovery. This added acid also causes corrosion problems.
While the rate at which corrosion will occur depends on a number of factors such as metallurgy, chemical nature of the corrosive agent, salinity, pH, temperature, etc., some sort of corrosion almost inevitably occurs. One way to mitigate this problem consists of using corrosion inhibitors in the hydrocarbon production system.
Corrosion inhibitors are widely used in oil and gas production wells and pipeline transmission lines. The corrosion inhibitors are generally high viscosity liquids. In order to form a pumpable product, a solvent is usually used to dilute the inhibitors and form a relatively low viscosity fluid. In general, the use of a large amount of solvent is undesirable since it increases the product cost and may contribute to flammability.
It is known that the corrosion of iron and steel alloys in contact with oil-in-brine emulsions can be inhibited by treating the emulsions with a water soluble polymer, specifically water soluble anionic, non-ionic and cationic polymers and/or nitrogen-containing corrosion inhibitors.
A microemulsion is a thermodynamically stable fluid. It is different from kinetically stable emulsions which will be break into oil and water over time. Water-in-oil microemulsions have been known to deliver water soluble oil field chemicals into subterranean rock formations. Also known are oil-in-alcohol microemulsions containing corrosion inhibitors in anti-freeze compositions.
It would be advantageous if a new corrosion inhibitor were discovered that would be an improvement over the presently known systems. It is always desirable to produce greater corrosion inhibiting ability using less corrosion inhibiting material and/or less inert material, particularly if the inert material is relatively expensive. It would also be useful if the corrosion inhibitor was stable during storage and reduced in flammability as compared with conventional corrosion inhibitors.